Pulse-jet units or thermo-propulsive pulsatory discharge nozzles with reversed admission orifices



Jan. 5, 1960 P. sERvANTY EI'AL PULSE-JET UNITS 0R THERMo-PRoPULsIvE PuLsAToRY DISCHARGE NozzLEs WITH REvERsED ADMISSION oRIFIcEs Filed Sept. 9, 1955 5 Sheets-Sheet 1 N @I L I l` fu N J'ncauss LEGRAND ALA/N Bozgc,

m TTDRNEYS Jan. 5, 1960 P. sERvANTY ETAI- 2,919,542

PULSE-JET UNITS OR THERMO-PROPULSIVE PULSATORY DISCHARGE NOZZLES WITH REVERSED ADMISSION ORIFICES 5 Sheets-Sheet 2 Filed Sept. 9, 1955 I'NVENToRs PIERRE SERVANTY PIERRE LE Rouzo 6ns-ro- Bouc HET Tncauss LESRAND B ALAIN Boze-c .9i/212401 4., M v7/220W ATTURNEYS Jan. 5, 1960 P. sERvANTY ETAI- PuLsEJET UNITS oR THERMo-PRoPuLsIvE PuLsAToRY DISCHARGE NOZZLES WITH REVERSED ADMISSION ORIFICES 5 Sheets-Sheet 3 Filed Sept. 9. 1955 INVENToPs PIERRE .SERV/surf 'PIEQRE LE Rouzo GASTON'BOUCHET JACQUES LEG-RAMI) ALAIN IBOZEC ATTORNE YS Jan. 5, 1960 P. sERvANTY EVAL 2,919,542

PULSETJET UNITS 0R THERMO-PROPULSIVE PULSATORY y DISCHARGE NozzLEs WITH REvERsED ADMISSION oRIFIcEs Filed Sept. 9. 1955 5 Sheets-Sheet 4 lNvENToRs PlERRE SERVANTY PIERRE LE ROUZO GASTON BOUCHET THCOUES LEGRAND :B A LA IN ,'BOZEC Wam, (2,5., M wy/f1 Jan. 5, 1960 P. sERvANTY ETAI- 2,919,542

PULSE-JET UNITS OR THERMO-PROPULSIVE PULSATORY DISCHARGE NOZZLES WITH REVERSED ADMISSION ORIFICES 5 Sheets-Sheet 5 Filed Sept. 9, 1955 n mvENTo S Y Hem u E R ADH R V CGC D RRUEE n EsoLz AJ SLB s o .H u E B R m n a m 53 PPG T A 0 Y B United States Patent PULSE-JET UNITS R THERMO-PROPULSIVE PULSATORY DISCHARGE NOZZLES WITH REVERSED ADMISSION ORIFICES Application September 9, 1955, Serial No. 533,282 `Claims priority, application France April 28, 1955 9 Claims. (Cl. 60-35.6)

, The technical development of pulse-jet units or discharge nozzles with pulsatory combustion without moving parts, has led to the development of a special class of these propulsive engines, which class is mainly characterised by the fact that the intake of the air required for the combustion is effected through the medium of a nozzle,the orifice of which, opening directly to atmosphere, is arranged to face in the opposite direction to the action of the thrust applied by the propulsive unit. The result of this is that, when `the device is in motion, the admission of air takes place in opposition to the normal air iiow. In order that the atmospheric air may reach the part of the device in which the injection of fuel takes place, this air must be subjected to a deflection of about 180 with respect to its initial direction, as shown in Fig. l of the attached drawings which illustrate a device in cross-section in which a is the pulsatory combustion chamber, b is `the discharge nozzle or exhaust pipe for the gases generated in this chamber by the successive combustions, and c is thetubular admission member for fresh air, designed to function as a valveless nonreturn admission orifice. It will be seen that, by reason of the 180 bend which exists at d between the chamber a and the discharge nozzle b, the tubular member c has its opening on the same side as the discharge nozzle. The arrow F indicates the direction of motion produced, while the arrow F1 shows the curved path which the relative air flow must follow in order to pass into the tubular admission member c.

, By reason of this particular feature, this class of pulse- ]'et units, which gives excellent performances under static conditions in an undefined atmosphere, is subject to substantial losses of performance when in motion. In addition, their general shape which is imposed on the one hand by specific requirements and, on the other hand, by technical reasons connected with the utilisation of materials at high temperatures, results in a high resistance toforward motion which heavily affects adversely the general performance of the propulsion device. The application of these reaction motors to the propulsion of flying machines thus necessitates their association with a cowling, the robject of which is at the same time to reduce lthe drag and the losses due to the intake of air in a direction opposite to the normal ow, by reducing substantially the relative speed of the air in the zone of the intake orifice.

It is of course possible to place one or a number of pulse-jet units within the interior of a streamlined cowling or casing e (see Fig. 2) which extends as far as the vicinity of the plane containing the outlet orifices of the discharge nozzles, the admission of atmospheric air being effected through an orifice f formed at the forward extremity of the Cowling, the geometric section of the orifice being substantially less than the largest right-angle cross-section of the cowling. In this way', it is possible v to obtain lan* appreciable slowing-down of the rate of flow in the region of the air-intake orifices c of the pulsejet units, but the practical application of this arrangement comes up against the following difhculty:

The applicants have observed that pulse-jet units 0perating under static conditions give rise to periodic variations of pressure in the surrounding atmosphere, these variations being measurable at distances from the devices amounting to several times the diameter of their intake orifices. In addition, tests have shown that each time the surrounding atmosphere affected by this phenomenon is arbitrarily limited by placing physical walls in position so as to enclose the pulse-jet unit, there results a sharp fall in the force of thrust developed by the unit. It even happens that if the walls are too close together, it is not possible to obtain any stable operation. The loss of thrust thus recorded will of course diminish as the separation of the walls increases, together with a corresponding increase in the ratio between the internal rectangular cross-section of the cowling and the right-angle section of the air-intake orifice of the pulse-jet unit. However, for a right-angle section of the Cowling which represents fifty times the area of the intake orifice of the pulse-jet unit, this loss still amounts to about 10%.

It should be noted that, in the case of the families of pulse-jet units which have a high performance, the area of the intake orifice of the cowling may represent one quarter or more of the total frontal surface area of the device. If it is desired to limit to 10% the loss of thrust as compared with the possible static thrust in undefined atmosphere, it will thus be necessary to provide a cowling, the frontal cross-section of which is about twelve times the overall cross-section ofthe pulse-jet unit proper. The resistance to forward movement of the cowling would, of course, become entirely prohibitive in this case.

The present invention has for its object a Cowling arrangement which enables a slowing-down effect to be obtained in the flow of air in the vicinity of the air intake of the pulse-jet unit or thermo-propulsive discharge nozzle, having no appreciable wall effect, thus making compatible the production of a static thrust equal to the thrust in an undefined atmosphere with a reduced resistance to forward motion and with admissible losses at the air intake.

The special feature of this Cowling consists in that it is open or slotted laterally in the Vicinity of the transverse plane containing the air admission orifice of the pulse-jet unit, over the largest possible part of the periphery of the said orifice, and also in that it is combined with a conduit, the opening of which is located on the downstream side of the said admission orifice in the direction of flow of the external air, the opening of the conduit having a section larger than that of the said orifice and being enclosed by a rounded leading edge which comes into contact with the flow of air and which serves to produce in this flow a zone of high static pressure which results in a zone of low speed in the vicinity of the air intake.

At its forward portion, the Cowling may be closed or simply provided with ports to permit of the entry of cooling air, which is suitable in the case of devices intended for flight at moderate speeds. In the case of high-speed devices, the Cowling may also be freely open at its forward extremity and may comprise a diffuser which serves to slow-down and to compress the air passing into the Cowling, so as to give it a relatively high static pressure at the point of arrival of this air, through an annular passage in the air Cowling, in the zone which comprises the orifice of the air intake and the opening or the lateral notch in the Cowling.

Further special features of the invention will be brought out in the description which follows below with reference to the attached drawing, which is given by way of example, it being understood that the features simply shown 3 on the drawings will form part of the said invention in addition to those referred to in the description.

Figs. l and 2 are explanatory figures which have already served as illustrations for the preamble to the present description.

Fig. 3 is a view in longitudinal cross-section of one form of embodiment of the invention.

Figs. 4 to 7 are transverse cross-sections taken along the lines IV--IV, V--V, VI-VI and VII-VII, respectively.

Figs. 8 and 9 are longitudinal cross-sections of two further forms of embodiment.

Figs. l to 13 are cross-sections of Fig. 9 taken along the lines X-X, XI-XL XII-XII and XIII-XIII, respectively.

Fig. 14 shows an alternative form of construction with a cowling open at its forward extremity.

Figs. l to 19 are cross-sections of Fig. 14 taken along the lines XV-XV, XVI-XVI, XVII-XVII, XVIII- XVIII and XIX-XIX, respectively.

The first type of cowling shown in Figs. 3 to 7 is especially adapted for ight at moderate speeds (30 to 130 metres per second). This cowling comprises:

(l) A screening member 1, generally of light alloy and of streamlined form, which encloses fairly closely the elbow d and also the combustion chamber a, and is directly joined to the air-intake orifice of the combustion chamber.

(2) A member or conduit 1a, generally of light alloy, and forming roughly a body of revolution about the axis of the air intake c, having a streamlined external shape and a conical or cylindro-conical internal form, comprising an air-intake orifice 3 bounded by a rounded leading edge 4 located at a certain distance from the corresponding supply intake orifice 2, and preferably at one and a half times the diameter of the latter approximately, so that a wide lateral notch g is formed freelyopen about the orifice 2. It is desirable that the area of the right-angle cross-section of the intake orifice 3 should be between two and three times the area of the supply orifice 2 of the pulsatory chamber a and that the cross-section area of the outlet orifice 5 should be greater than that of the intake orifice 3, these proportions and arrangements being those which provide the best slowing-down effect in the vicinity of the air-intake orifice 2 for the speed of flight considered.

(3) A cowlingl member 6 enclosing fairly closely the whole or a part of the exhaust discharge nozzle b of the pulsatory chamber and coupled to the members 1 and 2 and by a portion 8 of hollow curvature, the radii of which decrease from the front up to the plane of the air-intake orifice 2, the radii increasing from the plane of the intake orifice 3 to the plane of the outlet orifice 5 of the cowling.

The general shape of the cowling is shown quite clearly by the cross-sections given in Figs. 4 to 7. At the for- Ward part of the cowling member 1 are formed one or a number of ports 9 which allow the entry of cooling air to the cowling. The evacuation of this air may be partly efr'ected through the slot 10 and partly through one or a number of ports 11 formed in the cowling 1 in the vicinity of the air-intake orifice 2, that is to say in an area of sub-pressure.

In the case in which the pulse-jet unit with its cowling is required to operate for long periods while stationary, it is an advantage to provide for the evacuation of the cooling air through a slot located in the immediate vicinity of the air-intake orifice 2, for example in the coupling radius 12 between the orice 2 and the cowling member 1. By virtue of the periodic zones of subpressure which are created in the plane of the orifice 2, this arrangement permits of a `circulation of cooling air v this member.

under the cowling, even when the device is in static operation.

The elements which play a principal part during the operation are the varying hollow curvature 8, which enables the air-intake orifice 2 to have a peripheral air supply which is as ample as possible, and the rounded leading edge 4 which produces a high static-pressure zone and, in consequence, a region of low speeds in the vicinity of the inlet orifice.

In the alternative form of embodiment shown in Fig. 8, the cowling is extended beyond the plane of the outlet orifice which is common to the discharge nozzle b of the pulsatory chamber and the cowling member 1a, in order to form a chamber 13 having a substantially constant right-angle section, the length of which is with advantage from four to five times the diameter of the air intake orifice 2 of the pulsatory chamber. This chamber 13 is extended to form a convergent portion 14. The optimum ratio between the area of the outlet section 15 of this convergent portion and the area of the rectangular cross-section of the chamber 13, is a function of the speed of flight for which the propulsion unit is designed to operate and diminishes with this speed.

In this alternative form, it is possible to obtain a substantial increase in the performance, as regards thrust, by introducing the fuel by means of an injector 16 in the interior space of the cowling member 1a, on the downstream side of the smallest right-angle section of The chamber 13 is the seat of an extremely turbulent periodic flow and the combustion takes place in this chamber with an excellent stability. In this alternative form also, it is desirable that at least the member 3 and 13 should be in refractory material.

The Figures 9 to 13 show an example of construction applicable to the special case in which the air-intake orifice 2 and the orifice 19 of the discharge nozzle b are located in the same plane. The whole of the pulse-jet unit is then contained in a cowling body 17 of light alloy, which is coupled to the two orifices 2 and 19 and comprises the coupling groove 19 which enables a peripheral supply of the two oriiices to be effected as in the case of the previous embodiments. The cowling body 17 is coupled to a second cowling member 20 through the medium of streamlined-section arms 2 2. The member 20 essentially comprises two conical or cylindro-conical nozzles 20a and 20b, the inlet orifices of which are defined by rounded leading edges and which are centered on the axes of the orifices 2 and 19, the right-angle sections of these inlet orifices having values which are preferably comprised between two and three times the right-angle section of the orifice of the corresponding propulsive discharge nozzle.

The member 20 is thus similar to an assembly of two superposed annular wings coupled together by a varying hollow curvature, the radius of which increases from the front towards the rear. As in the case of the preceding alternative form, the cross-sections of the outlets of the conical or cylindro-conical nozzles 20a and 20b should be greater than the respective right-angle cross-sections of the inlet orifices, and the member 20 may comprise to its rear the chamber 13 and the convergent section 14. Provision is then made for introducing fuel through the injectors 16 and 21 located on the downstream side of the smallest right-angle section of the nozzles 20a and 20b.

Figs. 14 to 19 show a second type of cowling which is more particularly adapted for flight at medium speeds to 240 metres per second). This cowling is composed:

1) Of a substantially annular cowling body 23, generally of light metal, centered on the axis of the intake orifice 2 of the pulsatory chamber and comprising at the front portion an intake orifice 25enclosed by a rounded leading edge 26 and followed by a diffuser 25a. cowling body 23 satisfies the following conditions:

(a) Its intake orice 2S is located on the upstream side of the elbow d of the pulse-jet unit.

(b) Its terminall section 27 is freely open and is located in the immediate vicinity of the plane of the intake orice 2 of the pulsatory chamber (Fig. 14 shows this terminal section 27 in the same plane as the orifice 2).

(c) The terminal section 27 has a total surface area which is substantially greater than that of the intake orice 25.

(d) The total surface area of the terminal cross-section 27 is comprised between six and ten times the rightangle section ofthe supply orice 2 of the pulsatory chamber.

(2) Of a cowling member 24 coupled to the member 23 and closely enclosing the whole or a part of the resonator or exhaust discharge nozzle b.

(3) Of members similar to those already described This with reference to the preceding embodiments and which will be found on the figures, provided with the same reference numbers.

During operation when the device is stationary, the air intake orice 2 sucks-in atmospheric air from the exterior of the cowling 23, since the static pressure of this air is greater than that of the air which could arrive at this air-intake orifice by passing through the orice 25 in the cowling 23, by reason of the inevitable losses of pressure along this latter path. At high speeds, on the contrary, there is a large ow inside the cowling 23, due to the frontal orifice 25 and this ow reaches the terminal outlet section 27 with a static pressure which is greater than that of the flow of exterior air. It is then the ow passing through the interior of the cowling 23 which mainly supplies the oriiice 2, the remainder being supplied by the exterior air slowed-down by the rounded edge 4.

What we claim is:

1. The combination of a pulse jet unit of the kind having an exhaust pipe and a reversed air-admission device, the ends of which face in the same direction toward the rear of said unit, with a cowling surrounding at least a part of said unit and ending at the transverse plane containing said end of the air-admission device to allow direct suction of ambient air by said device, and a tubular 45 member extending to the rear of said device in substantially coaxial relation therewith and having an inlet opening spaced from and facing toward said end of the device,

said inlet opening having an area substantially greater than the area of said end of the device and being surrounded by a rounded leading edge.

2. The combination of claim 1 wherein the cowling is substantially closed at the front to form a stream-lined leading end for the unit.

3. The combination of claim 2, further comprising air inlet passage means through the leading end of the cowling and air outlet passage means near the rear end of said cowling in the vicinity of the end of the air-admission device.

4. The combination of claim 1 wherein the surface of the cowling is shaped to include longitudinal grooves which increase in depth from the front of said cowling towards the end thereof proximate to the air-admission device.

5. The combination of claim 1 further comprising a common chamber into which both the tubular member and exhaust pipe discharge, fuel injecting means for carburetting the flow of fluid through said chamber whereby combustion of said fuel takes place therein, and nozzle discharge means connected with said chamber and opening to the atmosphere.

6. The combination of claim 5 wherein the fuel injecting means discharges into the tubular member upstream of the common chamber.

7. The combination of claim 1 wherein the cowling is open at the front and forms a ramming intake.

8. The combination of claim 7 wherein the cowling comprises an annular passage extending around the airadmission device.

9. The combination of claim 8 wherein the annular passage terminates in the vicinity of the transverse plane of the end of the air-admission device, through an annular slot.

References Cited in the tile of this patent UNITED STATES PATENTS 2,439,817 Mercier Apr. 20, 1948 2,449,022 Stalker Sept. 7, 1948 2,574,460- Bohanon Nov. 13, 1951 FOREIGN PATENTS 157,691 Australia July 16, 1954 158,296 Australia Aug. 17, 1954 497,124 Canada Oct. 27, 1953 

